The invention relates to a knock-in pin dowel. Knock-in pin dowels are normally made from plastic and are prefabricated with an expandable element already inserted to some extent into the dowel shell. The fitting of an article to a substrate takes place very easily, because the dowel only has to be inserted through the object to be fixed and then, with the aid of a hammer, the fitter strikes the head of the expandable element. This blow serves both to completely introduce the dowel shell and to subsequently expand the dowel shell by the expandable element driven into it.
Normally the dowel shell contains an expandable part, which has two diametrically arranged longitudinal slits, so that two segments are formed, which can be folded outwards. The expandable element is generally a nail having a sawtooth-like thread, the latter not impeding the knocking in process (DE-OS 26 07 338, DE-OS 39 12 749).
This type of dowel is generally used when concrete constitutes the substrate and in which relatively good, cylindrical drilled holes can be produced.
However, there are increasing numbers of building materials, in which the material is more loosely seated, so that it is not possible to produce precise dowel holes, e.g. hollow chamber blocks or stones or lightweight building materials. Thus, the knock-in pin dowel is not adequately secured in such building materials.
The problem of the invention is to provide a knock-in pin dowel, which ensures a good anchoring, even in unfavourable wall building materials.